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Does oxygen limit nitrogenase activity in soybean exposed to elevated CO 2 ?
Author(s) -
CEN Y.P.,
LAYZELL D. B.
Publication year - 2004
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2004.01229.x
Subject(s) - nitrogenase , nodule (geology) , glycine , dry weight , nitrogen fixation , zoology , chemistry , root nodule , carbohydrate , biology , food science , horticulture , botany , biochemistry , nitrogen , amino acid , paleontology , organic chemistry
Soybean ( Glycine max L. Merr) plants grown under control (360 µ mol mol −1 ) or elevated CO 2 concentration (800 µ mol mol −1 ) from 33 to 42 d after sowing were assayed for various components of in vivo nitrogenase activity to test the hypothesis that increasing carbohydrate supply to nodules would increase the potential (i.e. O 2 saturated) nitrogenase activity and impose a more severe O 2 limitation on both nodule metabolism and total nitrogenase activity. Within 51 h of elevated CO 2 treatment, significant increases relative to control plants were seen in total nitrogenase activity expressed per plant. After 6 d of elevated CO 2 , the total nitrogenase activity per plant was 18% higher than that in control. This was attributed to an initial increase in nodule size, and a subsequent increase in nodule number following plant exposure to elevated CO 2 . However, after 9 d of elevated CO 2 , the potential and total nitrogenase activities per gram nodule dry weight were lower, not higher than corresponding values in plants in the control treatment. These results did not support the hypothesis. It was concluded that the metabolic capacity of the control nodules were not limited by carbohydrate supply, at least at the assay temperatures employed here.